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- Steen, Robert O., et al.
(författare)
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The role of isomeric effects on the luminescence lifetimes and electrochemistry of oligothienyl-bridged dinuclear tris(2,2′-bipyridine) ruthenium(II) complexes
- 2008
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-0682. ; :11, s. 1784-1794
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Tidskriftsartikel (refereegranskat)abstract
- The luminescence lifetimes (in CH 3CN at room temperature) and electrochemical potentials (in CH 3CN) of a range of mono- and bis(bidentate) 2,2′-bipyridine-capped oligothiophene-bridged Ru II complexes based on the 6-(2-thienyl)-2,2′-bipyridine and 4-(2-thienyl)-2,2′-bipyridine motifs have been measured. The redox potentials occurred in a very narrow range and showed only small shifts from that of [Ru(bpy) 3] 2+, which indicates that the inductive effects of the substituents on the 2,2′-bipyridine ligands are very similar across this series. In the complexes that incorporated a bithiophene moiety the oxidation of the bithienyl group occurred at higher potentials than the metal-centered Ru III/II oxidation. No or very weak interaction between the metal cores in the dinuclear complexes was observed. It was found that the luminescence lifetimes of the complexes where the attachment point of the oligothiophene bridge is in the 4-position of a 2,2′-bipyridine ligand were extended compared to [Ru(bpy) 3] 2+, whereas the luminescence was very short-lived (<30 ns) or completely quenched in the complexes where the oligothiophene bridge was attached in the 6-position. The difference in lifetimes is probably due to steric interactions between the thienyl bridge and the auxiliary bipyridyl ligands, resulting in disturbances in coordination symmetry of the metal core.
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| 5. |
- Steen, Robert O., 1978-, et al.
(författare)
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Bis-cyclometallated Molecular Switches Based on 4,7-phenantroline and 1,5-naphthyridine Architecture
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Two new bis-terdentate ligands, 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline (L1) and 2,6-bis(6-(thiophen-2-yl)pyridin-2-yl)-1,5-naphthyridine (L2), capable of reversible double cyclometallation have been synthesized. Both syntheses proceeded via a Skraup synthesis followed by Stille cross-coupling with 2-thiophen-2-yl-6-tributylstannylpyridine to yield the final product. The Ru2(tpy)2-complex of L1 was shown to be capable of reversible cyclometallation, where the bis-cyclometallated (C,C) isomer of the complex had an oxidation potential of +249 mV while the oxidation potential of the doubly S-coordinated (S,S) complex was +987 mV. No ground state interaction between the Ru cores was however found. In theory the complex should display a third, mixed, state. An S,C-coordinated isomer would open the way for molecular electronic applications based on ternary logic. However, despite attempts the S,C-coordinated complex could not be generated.
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| 6. |
- Steen, Robert O., 1978-, et al.
(författare)
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Coordination-mode pH-activated Molecular Switches based on Ruthenium(II) Oligopyridine Complex Architecture
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A number of [Ru(tpy)L] complexes (where L is a ligand based on the 6-thien-2-yl-2,2’-bipyridine motif) have been generated to study the ability of this terdentate motif to switch between a N,N,C and a N,N,S binding mode as a function of pH and irradiation. Whilst the parent system 6-thien-2-yl-2,2’-bipyridine (1) displayed facile switching between the orange and purple forms, heavier analogues displayed sluggish switching – most likely resulting from a large moment of inertia about the bond between the S/C-bonded thiophene ring and the chelating bipyridine unit. Prototypic unsymmetrical bimetallic complexes (C7S and C7C) have been generated in order to test if the binding mode of the switching unit can affect the oxidation potential of the remote [Ru(bpy)2(L)] unit. The results of cyclic voltammetry studies suggest that only weak electronic coupling between the metal cores exists, and that the coordination mode (N,N,C or N,N,S) of the thiophene moiety only has a small effect on the oxidation potential of the [Ru(bpy)2(L)] unit.
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| 7. |
- Steen, Robert O., et al.
(författare)
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Syntheses of Three New Pyridyl Thienopyridine Ligands via the Hurtley Reaction
- 2012
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Ingår i: Journal of Heterocyclic Chemistry. - : Wiley. - 0022-152X .- 1943-5193. ; 49:6, s. 1290-1295
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Tidskriftsartikel (refereegranskat)abstract
- The tridentate pyridyl thienopyridines 5-phenyl-7-(pyridin-2-yl)thieno[2,3-c]pyridine (L1), 7-(pyridin-2-yl)-5-(thiophen-2-yl)-thieno[2,3-c]pyridine (L2) and 5,7-di(pyridin-2-yl)thieno[2,3-c]pyridine (L3) have been synthesized via the Hurtley reaction. L1 and L2 were synthesized by condensing 3-bromothiophene-2-carboxylic acid with phenyl-1,3-butanedione and 1-thienyl-1,3-butanedione respectively. L3 was synthesized by condensing 3-bromothiophene-2-carboxylic acid with benzoylacetonitrile. Ring closure and a subsequent Negishi or Stille cross-coupling afforded L1, L2, and L3 in an overall yield of 20, 3, and 6%, respectively.
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| 8. |
- Steen, Robert O., 1978-, et al.
(författare)
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Synthesis of the Pyridyl Thienopyridine Ligands 5-phenyl-7-(pyridin-2-yl)-thieno[2,3-c]pyridine, 7-(pyridin-2-yl)-5-(thiophen-2-yl)thieno[2,3-c]pyridine and 5,7-di(pyridin-2-yl)thieno[2,3-c]pyridine via the Hurtley Reaction
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The tridentate thienopyridines 5-phenyl-7-(pyridin-2-yl)thieno[2,3-c]pyridine (L1), 7-(pyridin-2-yl)-5-(thiophen-2-yl)thieno[2,3-c]pyridine (L2) and 5,7-di(pyridin-2-yl)thieno[2,3-c]pyridine (L3) have been synthesized via the Hurtley reaction. L1 and L2 were synthesized by condensing 3-bromothiophene-2-carboxylic acid with phenyl-1,3-butanedione and 1-thienyl-1,3-butanedione respectively. L3 was synthesized by condensing 3-bromothiophene-2- carboxylic acid with benzoylacetonitrile. Ring closure and a subsequent Negishi or Stille cross-coupling afforded L1, L2 and L3 in an overall yield of 20%, 3% and 6% respectively. The corresponding [Ru(tpy)L]n+ complexes were prepared and their electrochemical and structural properties were examined.
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